Purely one-dimensional ferroelectricity and antiferroelectricity from van der Waals niobium oxide trihalides

Intrinsic one-dimensional (1D) ferroelectric materials are rarely reported but are highly sought to break the size limit of nanostructured conventional ferroelectrics. Herein, we report a class of inborn 1D ferroelectric nanowires, namely 1D NbOX3 (X = Cl, Br, and I), that can be directly obtained from experimentally realized van der Waals crystals. In addition to the sizable spontaneous polarization, 1D NbOX3 exhibits low ferroelectric switching barriers, small coercive electric fields, and high critical temperature, governed by the hybridization of the Nb empty d orbitals and the O p orbitals (d0 rule). Moreover, the double-channel structure of 1D NbOX3 also enables the emergence of 1D antiferroelectric metastable states. Our findings not only propose a class of 1D ferroelectric materials toward the development of miniaturized and high-density electronic devices, but also pave an avenue of obtaining intrinsic 1D ferroelectrics from van der Waals crystals.

Chiral Symmetry Breaking in Liquid Crystals: Appearance of Ferroelectricity and Antiferroelectricity

The study of chiral symmetry breaking in liquid crystals and the consequent emergence of ferroelectric and antiferroelectric phases is described. Furthermore, we show that the frustration between two phases induces a variety of structural phases called subphases and that resonant X-ray scattering is a powerful tool for the structural analysis of these complicated subphases. Finally, we discuss the future prospects for clarifying the origin of such successive phase transition.

Niobium oxide dihalides NbOX2: a new family of two-dimensional van der Waals layered materials with intrinsic ferroelectricity and antiferroelectricity

A new group of two-dimensional layered materials with intrinsic ferroelectricity and antiferroelectricity are identified through first-principles calculations.

Self-organization into ferroelectric and antiferroelectric crystals via the interplay between particle shape and dipolar interaction

Ferroelectricity and antiferroelectricity are widely seen in various types of condensed matter and are of technological significance not only due to their electrical switchability but also due to intriguing cross-coupling effects such as electro-mechanical and electro-caloric effects. The control of the two types of dipolar order has practically been made by changing the ionic radius of a constituent atom or externally applying strain for inorganic crystals and by changing the shape of a molecule for organic crystals. However, the basic physical principle behind such controllability involving crystal–lattice organization is still unknown. On the basis of a physical picture that a competition of dipolar order with another type of order is essential to understand this phenomenon, here we develop a simple model system composed of spheroid-like particles with a permanent dipole, which may capture an essence of this important structural transition in organic systems. In this model, we reveal that energetic frustration between the two types of anisotropic interactions, dipolar and steric interactions, is a key to control not only the phase transition but also the coupling between polarization and strain. Our finding provides a fundamental physical principle for self-organization to a crystal with desired dipolar order and realization of large electro-mechanical effects.